[RFC PATCH v1 2/6] of/device: Don't back devices DMA with IOMMU if that's undesired by driver

[Dmitry Osipenko]

Respect device driver requirement for device DMA not to be implicitly
backed with IOMMU by skipping the backing setup for drivers that do not
want that.

Signed-off-by: Dmitry Osipenko <digetx at gmail.com>
---
 drivers/of/device.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/of/device.c b/drivers/of/device.c
index 33d85511d790..e70b7a886875 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -163,6 +163,13 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma)
 	dev_dbg(dev, "device is%sbehind an iommu\n",
 		iommu ? " " : " not ");
 
+	/*
+	 * Respect device driver requirement for device DMA not to be
+	 * implicitly backed with IOMMU.
+	 */
+	if (iommu && dev->driver->no_implicit_iommu)
+		iommu = NULL;
+
 	arch_setup_dma_ops(dev, dma_addr, size, iommu, coherent);
 
 	return 0;
-- 
2.18.0